1. Field of the Invention
The present invention relates to a body coil in the field of magnetic resonance (MR) and, particularly, to a body coil assembly and a method for generating a radio-frequency field by using the body coil assembly.
2. Description of the Prior Art
In magnetic resonance systems employing a vertical magnet (in which the direction of main magnetic field is perpendicular to Z axis), the body coils are divided into two parts disposed oppositely, i.e., they include a first coil 10 and a second coil 20 as shown in FIG. 1, and the distance between the first coil 10 and the second coil 20 is L. If the first coil 10 and the second coil 20, as shown in FIG. 1, are disposed oppositely one above the other, and a patient 5 lies horizontally therebetween, then the first coil 10 and the second coil 20 are referred to respectively as an upper coil and a lower coil. The first coil 10 and the second coil 20 can be arranged differently from that shown in FIG. 1, and in the present invention there is no restriction in this regard. For example, the coils can be arranged oppositely with one to the left and the other right with a patient standing therebetween.
As shown in FIG. 1, in the magnetic resonance system of vertical magnets, since it is necessary for the body coil to generate a uniform radio-frequency field in the enclosed space, the first coil 10 and the second coil 20 are symmetric. In a conventional magnetic resonance system, the transmitting power is fixedly and symmetrically distributed to the first coil 10 and second coil 20, i.e., each of the first coil 10 and the second coil 20 consumes half of the overall transmitting power.
In addition, in order to improve the signal-to-noise ratio of the received signals, a conventional magnetic resonance system generally uses measures for improving the scanning sequence, but such an approach is very complicated to implement and cannot save powers.